Semi-Bright Nickel Guide
NiMac Semi-Bright Systems
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Semi-Bright Nickel
NiMac Semi-Bright Systems
What is semi-bright nickel plating?
Semi-bright nickel is the term given to nickel deposits
containing less than 0.005% sulfur. Semi-bright
nickel usually forms the first layer in a multilayer nickel system,
providing a high purity nickel layer designed to significantly improve
the corrosion resistance of electroplated nickel/chromium deposits.
The largest use of semi-bright nickel is in high performance
automotive applications, although other uses can be found where highly corrosion
resistant nickel/chromium coatings are required, for example bathroom and kitchen.
Semi-Bright : The term semi-bright comes from the use of nickel baths to produce deposits with a low
sulfur content to help provide increased corrosion resistance in duplex nickel coatings. Very early duplex deposits simply
used dull nickel deposits that were polished prior to bright nickel plating. Additives such as coumarin were subsequently
used to improve deposit leveling. These early coumarin-type systems produced deposits which were smooth with a
columnar structure, giving a finish that ranged from matte to almost fully bright (brighter in low current density areas).
Hence they were christened semi-bright due to the hazy appearance of the deposit. Today most platers use non-coumarin
systems. Deposits from these newer systems can also range from full matte to almost fully bright. Despite the bright finish
that can be obtained with these systems, the description semi-bright has remained. Semi-bright nickel deposits are
characterised by having a sulfur content of <0.005%. Sulfur-free would perhaps be a better generic description.
Multilayer: Multilayer nickel can refer to duplex nickel layers, but often duplex nickel is supplemented by a third or even
a fourth layer of nickel. The third layer is either a microporous or microcracked top nickel layer or a high sulfur nickel layer
between the semi-bright and bright layers. Sometimes all four layers are used to provide maximum corrosion resistance
underneath the final layer of chromium.
High Sulfur Nickel; A high sulfur nickel deposit is sometimes used in multilayer nickel systems between the semi-bright and bright
nickel layers in specifications requiring service condition 5. The high sulfur layer is characterised by having a sulfur content of
>0.15% . This layer will account for less than 10% of the total nickel thickness.
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Multilayer Nickel Plating: In multilayer nickel plating, each nickel layer provides different properties. Specifically, each
layer has a different electrochemical potential. These differences in electrochemical potential are the main factor that
determines the corrosion resistance of the nickel/chromium layer. The potential differences between the layers can be
measured, usually by a method called the STEP test. Below is an overview of the corrosion mechanism which illustrates
how the different layer types affect the performance.
Microporous Nickel Corrosion: The use of a microporous nickel
layer over a duplex nickel further enhances the corrosion resistance
of a plated component. Instead of penetrating a single corrosion
site as illustrated, the corrosion current is distributed over many
smaller sites. This results in hundreds or thousands of smaller sites
which corrode much more slowly.
Barrier Layer Corrosion: Plating a single layer of nickel, such as bright
nickel, over a reactive metal such as steel or aluminum will provide
corrosion resistance to the part only so long as the barrier is intact.
Once the nickel barrier is penetrated, corrosion of the base metal
will begin.
Multilayer Nickel Corrosion: By plating two layers of nickel,
with the top layer being more active (i.e. less noble), a new level
of corrosion performance is reached. This is generally accomplished
by plating bright nickel over semi-bright nickel. Once the initial
bright nickel barrier is penetrated, the corrosion spreads laterally
instead of penetrating the less active semi-bright nickel layer.
The effect can be improved by plating a high activity/high sulfur
layer between the semi-bright and bright nickel layers. This high
sulfur layer will also corrode laterally, offering increased protection
of the semi-bright layer.
STEP: “Simultaneous Thickness and Electrochemical Potential“ is a method to measure the difference in electrochemical
potential between each of the layers in multilayer nickel deposits. This test measures the thickness of the relevant nickel layers
at the same time, hence the test title. Over time, the term STEP has become synonymous with the measurement of the
electrochemical potential difference rather than thickness.
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Semi-Bright Nickel
Plating To Specification
ASTM B 604, ASTM B 456 and ISO 1456 list the following service conditions for high performance nickel chromium plating.
Semi-bright nickel is used in the most demanding service condition applications, and typically constitutes 50 – 70% of
the total nickel thickness.
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Service Condition Number
Description
Details
SC5
Extended very severe
Service conditions that include likely damage from
denting, scratching and abrasive wear in addition
to exposure to corrosive environments where
long-term protection of the substrate is required;
for example, conditions encountered by some
exterior components of automobiles.
SC4
Very severe
Conditions that include likely damage from
denting, scratching and abrasive wear in
addition to exposure to corrosive environments;
for example, conditions encountered by exterior
components of automobiles and by boat fittings
in salt water service.
SC3
Severe
Exposure that is likely to include occasional or
frequent wetting by rain or dew or possibly
strong cleaners and saline solutions; for example,
conditions encountered by porch and lawn
furniture, bicycle and perambulator parts, hospital
furniture and fixtures.
SC2
Moderate
Indoor exposure in places where condensation or
moisture may occur; for example, in kitchens and
bathrooms.
SC1
Mild
Indoor exposure in normally warm, dry
atmospheres with coating exposed to
minimum abrasion.
Automotive: Cars and chromium have been linked together for decades. Reaching its peak in the flamboyant styling of the
1950’s, chromium wheels, trim and accents have historically been used by car designers to help impart a distinctive look to
their cars. In the 1980’s exterior chromium almost vanished, in part due to fashion, styling changes and weight reduction
efforts for improved fuel efficiency, but also because of concerns over quality, particularly problems with premature
corrosion. Since then, advances in plating technology have made it possible to dramatically improve the performance of
chromium plated parts.
One of the most signiticant advances was the increased use of semi-bright nickels. The high purity of this nickel layer
helped to spread corrosion laterally between the bright/semi-bright interface, thus delaying penetration to the base
material and extending component life. New semi-bright nickel systems also have excellent ductility (or elongation)
characteristics meaning that they prevent premature coating cracking on ‘flexible’ substrates such as plastic.
Plastic Exterior Trim : Perhaps the most visible and recognizable application of high performance nickel and
chromium plate is exterior automotive trim. Components include front grills, headlight bezels, wing mirrors and tailgate
handles, typically plated to service condition 4 using either a duplex or multilayer nickel system and finished with
microporous nickel and chromium. The most critical factors for semi-bright processes in this application are exceptional
deposit ductility and reproducible STEP potential.
Steel Bumpers: North America remains a major market for nickel/chromium plated
steel bumpers. Due to the positioning of a bumper on the vehicle, it is one of the
toughest applications the coating will have to withstand. Bumpers are plated to
service condition 5, using multilayer nickels and microporous nickel chromium
to achieve high performance. The demand on the semi-bright layer is to
deliver ultra high leveling and a consistent STEP potential.
Aluminum Wheels: Nickel/chromium plating
of aluminum wheels is a complex and
highly skilled procedure. The technology
involved in both the pretreatment and plating
must be robust and able to deliver consistent STEP results and bright covering power. When specified as original equipment
on a new vehicle, wheels will be plated to service condition 5 or even more stringent requirements, using multilayer nickel
and microporous nickel and chromium. This ensures that the customer receives aluminum wheels that not only look
spectacular in the show room, but continue to look good after many miles of driving.
Plumbing Applications: Zinc base diecastings and copper alloys can be cast into very intricate shapes and are extensively
used to manufacture equipment for bathroom/plumbing applications. However these metals are quite reactive and
therefore need good protection from the damp atmospheres found in these environments. The use of duplex nickel
is common to meet service condition 2 in these applications, providing corrosion protection for the base material.
This type of application puts high emphasis on leveling to smooth out polishing lines.
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Semi-Bright Nickel
NiMac SF
NiMac 456
Typical Application
POP, Steel Bumpers, Aluminum
Steel Bumpers, POP, ZBDC
Type
Non-Coumarin
Non-Coumarin
Leveling
High
Very High
Appearance
(Bright low to medium CD, semi-lustrous high CD)
Batch Purification
Infrequent
Infrequent
Typical STEP
140mV
140 mV
NiMac SF
Process Description : NiMac SF is a non-coumarin,
Recommended Application : Plating on plastics,
sulfur-free nickel plating process which produces a very
aluminum wheels and plating copper alloys.
ductile deposit with good leveling. Unlike coumarin
Typical Specification : ASTM B604 PL/Cu15a Ni30d
based semi-bright nickels, NiMac SF does not require
Cr r, PL/Cu15a Ni25d Cr mc/mp, ASTM B456 Cu/Ni15b
frequent batch purification treatments, resulting in less
Cr r ISO 1456 Al/Ni40d Cr mc/mp, Cu/Ni10b Cr r
down time, reduced labour and less waste. NiMac SF
Blend can be used as a single component additive to
replace the NiMac SF Maintenance, NiMac SF Leveler
and NiMac SF Ductilizer. NiMac SF Blend is specifically
formulated for use in facilities where auxiliary anodes
are extensively employed.
NiMac 456
Process Description : NiMac 456 is a non-coumarin,
Recommended Application : Steel bumpers,
semi-bright nickel designed specifically to provide
plating on plastics, copper alloys and zinc based
maximum leveling while still maintaining excellent
diecastings.
STEP and deposit ductility. NiMac 456 can be used
Typical Specification : ISO 1456 Fe/Ni35d Cr mp/mc
on all substrates including plastics, but is particularly
ASTM B604 PL/Cu15a Ni30d Cr r, PL/Cu15a Ni25d
suitable for applications requiring high leveling from
Cr mc/mp ASTM B456 Fe/Ni35d Cr mp/mc, Zn/Cu5
the semi-bright nickel layer, without the disadvantages
Ni15b Cr mp/mc, Zn/Cu5 Ni20b Cr r, Cu/Ni15b
associated with coumarin based additives. Depending
Cr mp/mc, Cu/Ni20b Cr r
on the application, NiMac 456 can operate as a single or
dual additive system.
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NiMac 604
NiMac 8105
POP, Aluminum
Steel Bumpers
Non-Coumarin
Coumarin
Medium
Very High
Even brightness across full CD Range
Semi-lustrous
Infrequent
Very Frequent
140mV
140mV
NiMac 604
Process Description : NiMac 604 is specifically
Recommended Application : Plating on plastics
designed for use on plastic substrates. The process
Typical Specification : ASTM B604 PL/Cu15a Ni30d
conforms to ASTM B604 for semi-bright nickel and
Cr r, PL/Cu15a Ni25d Cr mc / mp
provides a bright clean nickel layer across the full
current range even at extreme low and high current
density areas. Deposits are low in stress and are
extremely ductile.
NiMac 8105
Process Description : NiMac 8105 is a coumarin-based
Recommended Application : Steel bumpers
process which is approved for plating steel bumpers.
Typical Specification : ISO 1456 Fe/Ni35d Cr mp/mc
NiMac 8105 uses one additive to maintain the very high
ASTM B456 Fe/Ni35d Cr mp/mc
rates of leveling and the deposit STEP. NiMac 8105 can
also be used as an additive in other semi-bright nickel
solutions to increase deposit leveling. NiMac 8105 is
particularly recommended for applications requiring
high leveling from the semi-bright nickel layer, i.e.
polished steels. When using NiMac 8105 additive,
frequent carbon purifications are required to remove
organic breakdown products.
Coumarin is a chemical compound found in many plants.
It has a sweet scent, readily recognized as the scent of
newly-mown hay. It is used as a leveling agent in some
semi-bright nickel systems. Although this material gives
excellent deposit leveling and ductility, the breakdown
products are harmful to the process and the solution
needs regular full carbon purifications.
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Semi-Bright Nickel
Purification Of Semi-Bright Nickel Solutions
In order to maintain the desired deposit properties from some semi-bright nickel plating solutions, (eg NiMac 8105)
regular purifications to remove organic and inorganic contaminants are essential. Contamination may not only
change the cosmetic appearance of the semi-bright deposit, but also alter its performance characteristics. Changing
these characteristics may cause premature failure of the nickel/chromium plated layers in service. However, unlike
purification of other systems such as bright nickel plating solutions, there are some points which have to be taken
into account:
•
The use of sulfur containing liquid purifiers to remove metallic contamination such as copper and zinc must
not be used in semi-bright plating solutions.
•
The introduction of any additives from a non-recommended source, i.e. bright nickel additives, will effectively
render the semi-bright nickel solution unsuitable for multilayer nickel plating applications.
Removing Organic Contamination
Carbon Treatment: The usual signs of organic contamination in a semi-bright nickel solution are pitting, poor response
to maintenance additions and dark or dull deposits that cannot be corrected by the normal means. 1 kg per 1000 litres,
(2.0 lbs per 250 gallons) of activated carbon packed on to a filter will normally remove unwanted organics, but more serious
contamination may require full batch carbon treatment.
Ultra Violet (UV) Light Purification: One alternative to carbon treatment avoids the environmental, health and safety
issues associated with carbon treatment. The method is purification by the use of hydrogen peroxide in conjunction with
ultraviolet light (UV). It avoids operators having to physically handle the plating solution and carbon dust, as well as
avoiding the need to dispose of the nickel-contaminated carbon waste. As the system can be used on a continuous basis,
it also helps a plater to keep within pre-defined limits of contamination. The system works by using UV light to irradiate
hydrogen peroxide thus generating hydroxyl radicals. Hydroxyl radicals are very powerful oxdiants and react very rapidly
with bath organics, oxidizing them to carbon dioxide.
Removing Metallic Contamination
Plating Out Or Dummying: Metallic contamination should be kept to a minimum through effective rinsing of parts prior
to plating in the semi-bright plating solution. Iron, copper, zinc and lead are the most common metallic impurities in
semi-bright nickel and are removed by dummy plating at 0.5 A/dm2 (5 A/ft2).
Filtering: Prevention of build up in copper and zinc can be achieved by conventional plate out techniques or the use of a
special filter aid powder, NiMac MRP. This purifier can be used with semi-bright nickels without altering the deposits STEP
characteristics. When plating steel substrates, iron can be oxidized with hydrogen peroxide and filtered for removal.
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Which Bright Nickel?
In most applications, the semi-bright layer will be coated with a bright nickel which provides the final deposit leveling and
lustre. The choice of bright nickel will depend on the substrate and end use of the component. The NiMac range of bright
nickels includes systems that have been designed to complement the underlying semi-bright layer in applications such as
bright exterior automotive trim, plated aluminum wheels, steel bumper bars and plumbing fittings.
POP-Exterior/
Interior
NiMac Challenger Plus
NiMac Clarion II
NiMac Clarion 3
NiMac GB
!!
!!
!
Steel
Bumpers
Aluminum
Wheels
!
!
!
!!
!
Plumbing
Cu Alloys
Plumbing
ZBDC
!
!!
!
!
!
!!
NiMac Challenger Plus: NiMac Challenger Plus is a
NiMac Clarion 3: NiMac Clarion 3 is a non – PPS
high performance PPS-based system particularly
system designed for producing a highly leveled final
suited for applications requiring high leveling. NiMac
deposit on substrates such as plastics, copper alloys
Challenger Plus is approved for use as the bright layer
and zinc based diecastings. For such a high leveling
in the multilayer nickel plating of aluminum wheels.
system the deposit has very good ductility. The system
is low in harmful breakdown products meaning that
regular batch carbon treatments are not necessary.
NiMac Clarion II: NiMac Clarion II is an index based
system designed for producing a final deposit on
NiMac GB: NiMac GB is a high performance PPS-based
multilayer nickel plated plastics. It gives deposits
system particularly suited for plating metals that require
which have excellent ductility, with good brightness
the bright layer to have good leveling.
and leveling across the full current density range.
The system exhibits very good deposit ductility and
The system is low in harmful breakdown products
chromium receptivity. If required, NiMac GB can be
meaning that regular batch carbon treatments are not
used in low nickel formulations, reducing solution
necessary.
dragout costs.
Bright nickels are often classified as containing ‘PPS’ or ‘PPS-OH’ . Systems that are free from either of these chemicals are often
called non-PPS or Index systems. The primary advantage of PPS / PPS-OH systems are their ultra high leveling. The disadvantage
is that the breakdown products can be harmful to the bright nickel and lead to poor deposit ductility.
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Semi-Bright Nickel
Nickel Data & Facts
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Symbol
Ni
Atomic Number
28
Atomic Weight
58.69
Discovered
Cronstedt 1751
Electron Configuration
[Ar]4s23d8
Name Of Origin
German Nickel: Satan or Old Nick, also, from kupfernickel: Old Nick's copper
Isotopes
14 known isotopes, 5 stable and 9 unstable. Natural nickel is a mixture of the 5 stable
isotopes.
Properties
Melting Point 1453°C
Boiling Point 2732°C
Specific Gravity 8.902 (25°C).
Nickel is a silvery white metal that takes a high polish. It is hard, ductile, malleable and
ferromagnetic. It is a fair conductor of heat and electricity. Nickel is a member of the
iron-cobalt group of metals (transition elements). Exposure to nickel metal and its
soluble compounds should not exceed 1 mg/m3 (8 hour time weighted average for a 40
hour week). Some nickel compounds (nickel carbonyl, nickel sulfide) are considered to
be highly toxic or carcinogenic.
Uses
Nickel is used primarily for the alloys it forms. It is used for making stainless steel and
many other corrosion resistant alloys. Copper-nickel alloy tubing is used in desalination
plants. Nickel is used in coinage and for armor plating. When added to glass, nickel
compounds give a green color. Nickel plating is applied to metals to provide a protective
coating. Finely divided nickel is used as a catalyst for hydrogenating vegetable oils. Nickel
is also used in ceramics, magnets and batteries.
Sources
Nickel is commercially obtained from pentlandite and pyrrhotite. Nickel is also present in
most meteorites. Iron meteorites (siderites) may contain iron alloyed with 5-20% nickel.
Deposits of nickel ore are located in Ontario, Australia, Cuba and Indonesia.
Outlook
Nickel use is growing at about 4% each year with use of nickel-containing stainless
steel growing at about 6%. The fastest growth today is in the newly and rapidly
industrializing countries, especially in Asia. At the end of life (EOL), nickel-containing
products can be collected and recycled for re-use. Nickel is one of the most recycled
materials globally. It is collected and recycled, mostly in the form of alloys. About half
of the nickel content of a stainless steel product today will have come from recycled
sources.
Safety
Nickel has some properties which have led to its soluble salts being classified as
hazardous substances. Soluble nickel can, in certain circumstances be associated
with toxicity, carcinogenicity and with dermal sensitization. The nickel industry is
collaborating in the formal assessment of all the risks associated with nickel that is
currently being undertaken.
Most of the practical risks associated with nickel are seen in certain complex processes
used in nickel production and refining. The risks are well known and are managed and
controlled by specific workplace regulations.
NiMac Semi-Bright Nickels
High Performance Decorative Coatings
The “active” barrier,
between success and
failure!
Sometimes the difference between success
and failure in performance testing is just a few
millivolts. That’s certainly the case with semi-bright
nickels because they are not all developed to
deliver the highest degree of corrosion protection.
NiMac Semi-Bright Nickels are the exception.
The low stress deposits from NiMac Semi-Bright
Nickels consistently deliver STEP test values in
excess of 140mV, ensuring you meet the most
demanding corrosion specifications for today’s
critical decorative plating applications.
So when you need a 100% reliable semi-bright
nickel deposit, count on the company that says
“Yes We Can”. MacDermid.
Key Features
• Exceptional STEP performance
• Highly levelled and ductile deposits
• Active corrosion barrier
• Coumarin free additives
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